Abstract

We report the results of experimental and numerical studies of the maximum length of multi-span DP-QPSK DWDM communication lines (channel rate of 100 Gbit s{sup -1}) with 100-kmlong uniform and combined spans. The use of the combined spans (50 km of SSMF fibre and 50 km of NZDSF fibre) has allowed the maximum line length to be increased up to 6700 km, which is 60% higher than in the case of homogeneous SSMF- and NZDSF-based spans. (optical transmission of information)

The nonlinear interference noise power was measured experimentally as a function of the signal power and the length of the fibre coherent 100-Gbit s{sup -1} communication line, in which chromatic dispersion is not optically compensated. An expression was derived for the optimal signal power corresponding to a maximal excess of the measured optical signal-to-noise ratio (OSNR) over the OSNR required for conditionally error-free operation. The dependence of signal optimal power measured experimentally well agrees with the theoretical formula derived. (optical information transmission)

The properties of optical solitons in variable-dispersion fibreoptic communication lines in which distributed Raman amplification of optical signals is used are studied by numerical simulation. It is shown that solitons can serve as carriers of information in communication systems with a data transmission rate exceeding 10 Gbit s{sup -1}. (optical solitons)

We have studied experimentally and using numerical simulations and a phenomenological analytical model the dependences of the bit error rate (BER) on the signal power and length of a coherent single-span communication line with transponders employing polarisation division multiplexing and four-level phase modulation (100 Gbit s{sup -1} DP-QPSK format). In comparing the data of the experiment, numerical simulations and theoretical analysis, we have found two optimal powers: the power at which the BER is minimal and the power at which the fade margin in the line is maximal. We have derived and analysed the dependences of the BER on themore » optical signal power at the fibre line input and the dependence of the admissible input signal power range for implementation of the communication lines with a length from 30 – 50 km up to a maximum length of 250 km. (optical transmission of information)« less

The results of numerical modelling of nonlinear propagation of an optical signal in multimode fibres with a small differential group delay are presented. It is found that the dependence of the error vector magnitude (EVM) on the differential group delay can be reduced by increasing the number of ADC samples per symbol in the numerical implementation of the differential group delay compensation algorithm in the receiver. The possibility of using multimode fibres with a small differential group delay for data transmission in modern digital communication systems is demonstrated. It is shown that with increasing number of modes the strong couplingmore » regime provides a lower EVM level than the weak coupling one. (fibre-optic communication lines)« less